Many water or liquid impervious containers such as milk, orange juice and grapefruit juice cartons are manufactured by a process which involves folding a flat sheet of coated paperboard into a container shape. Since the blanks to be folded are typically cut from coated sheets of paperboard, at least one uncoated cut edge of the paperboard is typically exposed to the liquid in the formed container. Absorption of the liquid can occur at this uncoated cut edge while the carton is at rest or as a result of vibrational and other forces generated during shipping and handling. When the liquid penetrates or wicks through this uncoated edge the carton may lose structural strength and containment integrity and thus may leak. A method for testing coated paperboard in a paper mill environment is therefore beneficial as a quality control measure to assess the susceptibility of the paperboard to wicking and subsequent failure.
There are presently several methods and apparatus for determining the wicking properties of materials. One method involves inserting a doughnut-shaped web sample into a device so that only the cut edges of the web are in contact with a liquid in a chamber, filling the chamber and a calibrated capillary tube with the liquid, and measuring the rate at which the liquid is drawn down through the sample. In this method only ambient pressure is applied to the test liquid and chamber and there are no means for accelerating the test to reduce the testing time. Furthermore the test fails to provide a means for simulating vibrational forces generated during transportation and handling of paperboard containers. Additionally, this test method requires filling and emptying the liquid reservoir for each test.
It is, therefore, an object of the present invention to provide an improved web wicking apparatus and method for testing a web at its production site.
Another object of the present invention is to provide a simple web sample preparation method and mounting procedure for testing the wicking properties of a web.
A further object of the present invention is to provide computer automation of all phases of the test procedure, including overall assessment of the web's wicking characteristics.
An additional object of the present invention is to provide a test device and method adapted for use as a quality control measure for coated paperboard webs in a paper mill environment.
A still further object of the present invention is to provide an apparatus and method for simulating vibration levels that paperboard containers experience during shipping and handling.